Re: [Dovecot] Released v1.1.beta3

"/usr/include/sys/feature_tests.h", line 336: #error: "Compiler or options invalid; UNIX 03 and POSIX.1-2001 applications require the use of c99"

You'll need to enable C99 support. I think it was -xc99 or -std=c99 or something like that. man cc should help.